Question about Wayland dependancies

[David Herrmann]

Hi Walter

On Sat, Sep 22, 2012 at 5:25 PM, Walter Dnes <waltdnes at waltdnes.org> wrote:
>   I don't know if this is the correct list to ask this question.  If
> not, please let me know the correct list.  According to Wikipedia
> http://en.wikipedia.org/wiki/Wayland_%28display_server_protocol%29
> Weston depends on udev.

Udev is used in Weston to support device-hotplugging. If your system
uses other device-hotpluggin mechanisms, it is very straightforward to
support them, too. The Wayland architecture doesn't require udev.
However, all developers working on Weston probably use systems with
udev so nobody cared, yet.

Furthermore, Pekka ported Weston to Android (which doesn't use udev
natively). I think he made it work without udev so your concerns are
really not needed.

> This was not an issue when Wayland was
> originally conceived, but things have changed over the years.  udev
> has been rolled into the systemd tarball, and shares common code.  I
> don't want to get into the "separate /usr holy-war".  This goes beyond
> that.  Down the road, udev will be systemd-only.  I know about the
> promises of compatability for non-systemd systems, but... I suggest you
> read the message straight from the source...
>
> http://lists.freedesktop.org/archives/systemd-devel/2012-August/006066.html
>> Well, we intent to continue to make it possible to run udevd outside
>> of systemd. But that's about it. We will not polish that, or add
>> new features to that or anything.
>>
>> OTOH we do polish behaviour of udev when used *within* systemd
>> however, and that's our primary focus.
>>
>> And what we will certainly not do is compromise the uniform
>> integration into systemd for some cosmetic improvements for
>> non-systemd systems.
>>
>> (Yes, udev on non-systemd systems is in our eyes a dead end, in case
>> you haven't noticed it yet. I am looking forward to the day when we
>> can drop that support entirely.)
>>
>> Lennart --
>> Lennart Poettering - Red Hat, Inc.
>
>   So today, non-systemd systems are already 2nd-class citizens of udev,
> and down the road udev will only run under systemd.  This implies that
> Weston will be restricted to systemd-only.  Is that the way you want to
> go?

I don't know why everyone went crazy after Lennart posted this, but
there is really no need to worry. If (and this is a _big_ IF) udev
will depend on systemd at some time, then it is really easy to simply
fork udev and maintain it for all the other systems that do not use
systemd. Anyway, this discussion doesn't belong to this list.

>   IANACP...  I Am Not A C Programmer.  I've been following the list for
> a few weeks to get some background of the situation.  I notice
> references to evdev.  A while ago, evdev became dependant on udev.  I'm

I guess you're talking about Weston evdev.c? It's not the only part
that uses udev, btw. However, as said earlier, this is really no
requirement.

> currently running Gentoo linux with mdev as a udev replacement on 3
> machines.  X and ICEWM work fine.  See...
> https://wiki.gentoo.org/wiki/Mdev and
> https://wiki.gentoo.org/wiki/Mdev/Automount_USB   Do Weston/Wayland
> inherently requires udev/evdev?  If not, I'd like to experiment with it
> myself.  I am not a programmer, but I can...
> "./configure --with-various-options && make && make install".

Weston is still under heavy development. Every contribution is
welcome. However, you might need to find a developer who uses Gentoo
(or Mdev at least) to get support for it. But if the patches are
well-written, I think Kristian will apply them.

Regards
David